Attackers have fired a rocket at the US embassy compound in the centre of the Greek capital, Athens.

The rocket, fired from street level into the front of the embassy, caused minor damage to the building but no-one was injured.

The US envoy condemned the "very serious attack", as fire engines and police cordoned off the area.

Police say they are investigating claims that a left-wing radical group was behind the attack.

An anonymous phone call to the authorities said a group calling itself Revolutionary Struggle was responsible.

Revolutionary Struggle has carried out several bomb attacks in Athens since the demise of November 17, a left-wing group which terrorized Greece for 25 years before being dismantled in time for the 2004 Athens Olympics.

'Windows shattered'

The blast was reported in the early morning at the embassy, which is on one of Athens' main boulevards.

Police said a rocket was fired at the US eagle emblem at the front of the building.

"A self-propelled explosive was fired at 5:58 am (0358 GMT) from the surrounding area, causing minor damage to the front windows and the roof," a statement from the Greek public order ministry said.

The rocket landed in a toilet on the third floor of the building, which also houses Ambassador Charles Ries's office.

"I am treating this as a very serious attack," he said. "The embassy was attacked in a senseless act of violence."

Television pictures showed a mass of emergency vehicles and stationary traffic outside the embassy as the area was sealed off.

"This is an act of terrorism," Attica Police Chief Asimakis Golfis told the Associated Press news agency.

The US embassy is one of the most fortified and tightly guarded buildings in the region and is frequently the target of protests in a country brimming with potent anti-Americanism, our correspondent says.

In February 1996, it suffered minor damage when unknown attackers - thought to be leftist radicals - fired a rocket at it.

In the past, the far-left November 17 group - now disbanded and whose leaders were jailed in 2003 - attacked Greek, US and other foreign targets, killing more than 20 people.

Photo caption

Police outside the US embassy in Athens